Electrodynamic loudspeaker



July 14, 1936.

P. R. DIJKSTERHUIS 2,047,361

ELECTRODYNAMIC LOUDSPEAKER Filed Jan. 21, 1932 13 14 a \flw 12 rFn n nrfn m INVENTOR POPKO REINDER DIJKSTERHUIS AI'TORNEY Patented July 14,1936 UNITED STATES PATENT OFFICE ELECTRODYNAMIC LOUDSPEAKER ApplicationJanuary 21, 1932, Serial No. 587,870 In Germany April 2, 1931 5 Claims.

This invention relates to an electrodynamic loudspeaker comprising amagnet, one of the pole pieces of which consists of a soft-iron ring.

According to the invention the ring and the magnet have clamped betweenthem the means of supporting the diaphragm. This ensures that specialmeans of attachment for the supporting members can be dispensed with andin addition that the clamping operation can be effected simultaneouslywith the placing in position of the ring. If, as is the practice, thering is pressed into the magnet this method will assist materially toreduce the time of manufacturing the loudspeaker, also because anyscrews of attachment can be dispensed with, which is very important whenloudspeakers of the said kind are to be produced in bulk.

The idea of the invention is preferably applied to loudspeakersfurnished with a conical diaphragm the edge of which is secured to acarrier by means of a resilient substance. In such a case the carrier isclamped to the magnet system in the manner above referred to. In thesaid construction, this has the advantage of permitting during assemblyof first suspending in the magnet the ring and the carrier and thensuspending in the carrier the cone to which the coil for the speechmodulated currents is attached and also the means for centering it.

In order that the invention may be clearly understood and readilycarried into effect one construction in accordance therewith will now bedescribed more fully with reference to the accompanying drawing. 7

In the figure, I designates a permanent magnet the pole pieces of whichare formed by a soft-iron ring 2 and a soft-iron central stud 3 whichare arranged relatively to each other to form an air gap 4. A coil 6 forthe speech modulated currents which is secured to a conical diaphragm 5is arranged in the said air gap in which it is kept centered, forexample, by a flexible hood-shaped body "i, having its flange shapededge 8 glued to the cone and being centrally fixed to the central poleby means of a small bolt 9.

The edge ID of the cone 5 has glued to it a strip I l of a yieldingsubstance, say thin leather, which has its edge l2 clamped by means ofsmall bolts l3 between a metal ring it and the edge l5 of a metal frameIt. This frame is in the shape of a 'frustrum and is provided withspokes l'l united on the underside by an annular part I8 which accordingto the invention is clamped between the ring 2 and the magnet I. Theclamping is efiected. by pressing the ring and the flange N3 of the thelateral wall which is situated in the neighbourhood of the air gapconsists of a soft iron ring having such a section that the anglesformed by the upper and the lower surface of the ring and the upper sideand the lateral side of the stud which are at right angles to each otherrespectively are substantially equal. This construction has a greatadvantage in that the stud can have the usual cylindrical form that isto say such a form that from the point of attachment in the box itgradually decreases in section so as to have at least in theneighbourhood of the air gap, and throughout constant sections. A studwhich is so constructed is preferable to a stud the cross section ofwhich is larger near the gap than at the other points, as with a givenvolume of the gap the height of the latter depends on the diameter ofthe stud in the neighbourhood of the air gap and on the width of the airgap, and the height cannot be too small as in this case the leakagecoefficient would receive an excessive value.

Having now described my invention what I claim is:

1. An electrodynamic loudspeaker comprising a magnet one of the polepieces of which consists of a soft-iron ring, and means for supportingthe loudspeaker diaphragm clamped between the ring and the magnet.

2. Electrodynamic acoustic apparatus comprising a magnet system, adiaphragm, and a rigid member extending from said magnet system to theperipheral edge of said diaphragm for supporting said diaphragm, saidrigid member including a flanged portion, and a flange on a part of saidmagnet system adapted to clamp the 5. Electro-dynamic acoustic apparatuscomprising a magnet system, said magnet system including at least twoparts connected in series with respect to the flow of magnetic fluxtherethrough, a diaphragm, and a housing for said diaphragm having aportion clamped between said two parts of the magnet system and retainedthereby solely by friction, said housing being adapted to support theperipheral edge of said diaphragm.

POPKO REINDER DIJKSTERI-IUIS.

